Led illumination device with cubic zirconia lens

ABSTRACT

A lens element has a curved surface mounted adjacent an LED for improving the light transmission efficiency and the dispersal pattern of radiation emitted by the LED.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims benefit under 35 USC Sections 119(e) and 120 tothe filing date of U.S. Provisional Application Ser. No. 60/652,317filed by Mark S. Olsson on Feb. 10, 2005.

FIELD OF THE INVENTION

The present invention relates to lighting, and more particularly, toillumination devices that use light emitting diodes (LEDs) as a sourceof light.

BACKGROUND OF THE INVENTION

Semiconductor LEDs have replaced conventional incandescent, fluorescentand halogen light sources in many applications due to their small size,reliability, relatively inexpensive cost, long life and compatibilitywith other solid state devices. In a conventional LED, an N-type galliumarsenide substrate that is properly doped and joined with a P-type anodewill emit light in visible and infrared wavelengths under a forwardbias. In general, the brightness of the light given off by an LED iscontingent upon the number of photons that are released by therecombination of carriers inside the LED. The higher the forward biasvoltage, the larger the current and the larger the number of carriersthat recombine. Therefore, the brightness of an LED can be increased byincreasing the forward voltage. However due to many limitations,including the ability to dissipate heat, conventional LEDs are onlycapable of producing about six to seven lumens.

Recently a new type of LED has been developed for use as a flash incamera phones. The Luxeon® Flash LXCL-PWF1 and LXCL-PWF2 LEDscommercially available from Lumileds Lighting of San Jose, Calif., USAare capable of producing forty lumens at one ampere, and eighty lumensat one ampere, respectively. These surface mounted LEDs are only onemillimeter in height and they have a very small footprint (2.0×1.6 mm or3.2×1.6 mm, respectively). They are rated for 100,000 flashes at oneampere, and one hundred and sixty-eight hours of DC (flashlight/torchmode) at 350 milliamperes.

While these new flash LEDs offer increased brightness over conventionalLEDs they still suffer from problems associated with heat dissipationand inefficient distribution of light.

SUMMARY OF THE INVENTION

In accordance with an embodiment of the invention an illumination deviceincludes an LED and a lens element with a curved surface positionedopposite a light emitting surface of the LED. A quantity of transparentmaterial joins the lens element and the light emitting surface of theLED.

In accordance with another embodiment of the invention an illuminationdevice includes at least one LED mounted on a substrate and having anexposed metal heat conduction surface. At least one aperture is formedin the substrate adjacent to the exposed metal heat conduction surfaceof the LED and a heat sink is mounted in the aperture.

In accordance with another embodiment of the invention a method offabricating an illumination device includes the steps of removing a topsection of an optically transparent cover of a high intensity LEDpackage and leaving a remaining lower section having a height dimensionless than about twice a longest dimension of a light emitting surface ofan LED in the LED package. The method further includes the step ofmounting a lens element on top of the lower section, the lens elementhaving a curved surface that faces the light emitting surface of theLED.

BRIEF DESCRIPTION OF THE DRAWINGS

Throughout the drawing figures, like numerals refer to like parts.

FIG. 1 is a diagrammatic side view of an embodiment of the presentinvention.

FIG. 2 illustrates the light focusing properties of the embodiment ofFIG. 1.

FIG. 3 illustrates another embodiment in which the LED and thetransparent element are surrounded by a metal face plate.

FIG. 4 illustrates another embodiment similar to that of FIG. 3 exceptthat the transparent element is formed as a truncated ball lens.

FIG. 5 illustrates another embodiment similar to that of FIG. 3 exceptthat the face plate has a spherical ball support.

FIG. 6 illustrates another embodiment with reflectors.

FIG. 7 illustrates another embodiment with a thermal fluid.

FIG. 8 illustrates another embodiment with an anodized Aluminum faceplate.

FIG. 9 illustrates another embodiment with a thermal cup.

FIG. 10 illustrates another embodiment with a steerable beam.

FIG. 11 illustrates an alternate embodiment with a steerable beam.

FIG. 12 illustrates another embodiment with a hemispherical lens.

FIG. 13 is an isometric view of a prior art LED and lens assembly.

FIG. 14 is a vertical sectional view through the prior art LED and lensassembly of FIG. 13.

FIG. 15 is an isometric view of an LED and spherical lens assembly inaccordance with another embodiment of the present invention.

FIG. 16 is a vertical sectional view through the LED and spherical lensassembly of FIG. 15.

FIG. 17 is an isometric view of another embodiment of the presentinvention similar to FIG. 15 in which the top of the spherical lens hasbeen truncated.

FIG. 18 is a vertical sectional view of the embodiment of FIG. 17.

FIG. 19 is an isometric view of another embodiment of the presentinvention in which the lens comprises half of a sphere, with a flatsurface facing upwardly.

FIG. 20 is a vertical sectional view through the embodiment of FIG. 19.

FIG. 21 is an isometric view of another embodiment in which the lenscomprises half of a sphere, with the flat surface facing downwardly.

FIG. 22 is a vertical sectional view of the embodiment of FIG. 21.

FIG. 23 is an isometric view illustrating the manner in which a portionof a commercially available high intensity LED assembly may be removed.

FIG. 24 is a vertical sectional view illustrating the removal of a partof a commercially available high intensity LED with a blade.

FIG. 25 is a side-elevation view illustrating the dimensionalrelationships of another embodiment of the present invention thatemploys a spherical lens element.

FIG. 26 is a vertical sectional view through another embodiment of thepresent invention similar to the embodiment of FIG. 25 and in addition,employing heat sinks.

FIG. 27 is a part vertical section, part side elevation view of theembodiment of FIG. 26.

FIG. 28 is a part vertical section, part side elevation viewillustrating another embodiment of the present invention particularlysuited for underwater use.

FIG. 29 is a part vertical section, part side elevation view of anotherembodiment of the present invention employing a diverging opticalelement having a negative focal length.

FIG. 30 is a part vertical section, part side elevation view of anotherembodiment of the present invention employing a second optical elementin the form of a prismatic lens.

FIG. 31 is a part vertical section, part side elevation view of anotherembodiment of the present invention suited for a hidden flush mountapplication.

FIG. 32 is a part vertical section, part side elevation view of anotherembodiment of the present invention with a second optical element havinga hemispherical socket for receiving a spherical lens element.

FIG. 33 is an isometric view of a thru-hull light constructed inaccordance with the present invention.

FIG. 34 is a side elevation view of the thru-hull light of FIG. 33.

FIG. 35 is an exploded isometric view of the thru-hull light of FIG. 33.

FIG. 36 is a vertical section view of the thru-hull light of FIG. 33,taken along line 36-36 of FIG. 34.

FIG. 37 is a top plan view illustrating the arrangement of LED lightassemblies within the thru-hull light of FIG. 33.

FIG. 38 is an isometric view of another embodiment of the presentinvention that utilizes a rod lens element.

FIG. 39 is a vertical section view through the embodiment of FIG. 38.

FIG. 40 is an isometric view of another embodiment of the presentinvention that utilizes a rod lens element with rounded upper and lowerends.

FIG. 41 is a vertical section view through the embodiment of FIG. 40.

DETAILED DESCRIPTION

The entire disclosure of Provisional Application Ser. No. 60/652,317 ofMark S. Olsson filed Feb. 10, 2005, is hereby incorporated by reference.

Referring to FIG. 1, a flash LED 10 is surface mounted on a circuitsupporting element 14 in the form of a planar printed circuit board(PCB). A flat facet (not visible) of a substantially spherical opticallytransparent element 12 measuring approximately 3/16 inches in diameteris bonded to the active upper face of the flash LED 10. One suitablecommercially available adhesive is transparent, high temperatureadhesive designated Loctite 382 (Tak Pak). The flash LED 10 ispreferably the previously identified Luxeon® Flash LXCL-PWF1 LED orLXCL-PWF2 LED commercially available from Lumileds Lighting. Furtherdetails of these LEDs may be found in the list of issued U.S. patentsand pending U.S. patent applications set forth in Appendix A of theaforementioned provisional application, the entire disclosures of whichare hereby incorporated by reference. The optically transparent element12 is preferably made of sapphire. The total light output of the deviceillustrated in FIG. 1 was found to be approximately fifteen percentgreater than the flash LED 10 by itself. It is believed that thisincrease in total light output is due to improved heat dissipation fromthe front side of the emitter of the flash LED 10 and the regionimmediately around the emitter due to the proximity of the sapphireelement 12, which is an excellent conductor of heat. Unlike conventionalLEDs, the flash LED 10 is not bonded directly to a massive metalsubstrate so the sapphire element 12 provides alternate means of heatremoval from the flash LED 10. In addition, the sapphire element 12 canaffect the radiation emitted by the flash LED 10 by focusing the sameinto a beam.

Besides sapphire, transparent ceramics such as Magnesia (MgO), magnesiumaluminate spinel (Mg Al2O4), aluminum oxynitride spinel (AlON), cubiczirconia (ZRO2Si), spinel (MgO x Al2O3) and rutile (TiO2) can also beused for the transparent element 12 due to their a high thermalconductivity. It is preferable that the transparent element 12 be madeof a material that has at least half or more of the thermal conductivityof sapphire. Sapphire has an additional advantage of having a high indexof refraction, such that when element 12 is made of properly shapedsapphire, it can focus the radiation emitted by the flash LED 10 into ahighly useful slightly diverging beam

Heat transfer is improved by using a body 16 of an optically transparentmaterial to thermally couple the flash LED 10 and the transparentelement 12. The body 16 may be transparent fluid, grease, gel orpolymer. One suitable material is DOW CORNING® compound 4 (DC 4) whichis stable up to four hundred degrees F. (204 C.) which is above themaximum operating temperature of the flash LED 10. Certain fluorocarbonthermal management fluids such as 3M Novec® Engineered Fluids (HFE-7200)or 3M Fluorinert® Electronic Liquids. HFE-7000 has a boiling point of 76C., which is well below the operating temperature of the flash LED 10.Boiling off of the cooling fluid, on and adjacent to the flash LED 10can provide significant additional cooling. For additional coolingforced fluid flow and channels can be provided adjacent the flash LED10. The flash LED 10 and body 16 can be pressed against the base of thetransparent element 12 with a spring or using the resilience of the PCB14, as indicated by the arrows 18.

FIG. 2 illustrates the manner in which the generally sphericaltransparent element 12 forms the radiation emitted by the flash LED 10into abeam represented by light rays 30. The gap between the face of theflash LED 10 and the underside of the transparent element 12 is filledwith a transparent grease or gel 32.

A low melting point metal could also be used as a heat conductingelement all around the sides of the flash LED 10. Metals such as bismuthor gallium with a melting point well below the maximum operatingtemperature of the flash LED 10 can be used. Among these are tenspecialty solders commercially available from Indium Corporation ofAmerica having melting points below 140 degrees C.

Another aspect of the present invention involves press fitting asapphire sphere or a modified sapphire sphere into a surrounding metalstructures. High thermal conductivity metals such as copper, brass,bronze and aluminum are particularly suitable in this application, butother metals such as stainless steel and titanium may suffice inparticular environments. A press fit provides an optimal thermalcoupling between the sapphire element and the metal structure. The metalstructure may be in thermal contact with other structures to providegreater heat sink capabilities. Referring now to FIG. 3, a sapphiresphere 12 is press fit into a cylindrical bore in a metal face plate 40.Optionally, a sealant 42 fills the peripheral gap between the upper sideof the sapphire sphere 12 and the upper surface of the face plate 40. Atits largest outside diameter 44 the sapphire sphere 12 engages the wallof the bore in the metal faceplate 40, the tolerances being controlledto provide a snug fit. The sapphire sphere 12 is press fit into closeproximity with the upper active face of the flash LED 10, but not incontact therewith. The region of the bore in the metal faceplate 40beneath the sapphire sphere 12 and between the sphere 12 and the flashLED 10 are filled with transparent grease or gel 16. Arrows 46illustrate the flow of heat from the flash LED 10 into the sapphiresphere 12 and from the sapphire sphere 12 into the surrounding metalface plate 40. Arrows 48 illustrate the flow of heat through the frontor upper side of the sapphire sphere 12, which acts as both a heat sinkand a lens, into the gas or liquid above the sapphire sphere 12.

FIG. 4 illustrates another embodiment similar to that of FIG. 3 exceptthat the transparent element is formed as a truncated ball lens 50. Itsupper flat surface forms a wider beam of radiation.

FIG. 5 illustrates another embodiment similar to that of FIG. 3 exceptthat the bore in the metal face plate 60 is formed with a curvedshoulder 61 that supports the underside of the sapphire sphere 12 inprecise position in close proximity to the flash LED 10. Thus aso-called “ball mill plunge cut” in the metal face plate 60 can providean advantageous mounting for the sapphire sphere 12. The curved shoulder61 provides a matched radius surface that increases the area of contactbetween the sapphire sphere 12 and the metal face plate 60. This type ofmounting also allows the sapphire sphere 12 to withstand high loads andpressures on the outside face and remain fully supported, as might beencountered in undersea applications. In this embodiment a quantity of asuitable transparent potting material 62 completely covers the upperside of the sapphire sphere 12 and has an upper surface flush with theupper surface of the metal face plate 60. Various other methods can beused to seal the bore, including glues, adhesives, potting compound,rubber gaskets, and elastomeric O-rings.

While press fitting the sapphire sphere has certain advantages, it isnot essential to the present invention. Other means for holding thetransparent element 12 in place can be used, be they mechanical oradhesive. A thermal shrink fit can also be employed. By way of exampleonly, mounting a sapphire sphere 12 in a bore in an aluminum alloy(7075, 6061 or 6262) or brass alloy (CA 360) with a press fit of aboutone percent smaller than the diameter of the pressed sphere has producedgood results. With softer materials press fits as high as two percenthave been successful.

FIG. 6 illustrates an alternate embodiment in which metal face plate 70has a counter-sunk bore, the outwardly tapered part 71 of which forms areflector. The sapphire sphere 12 is press fit into the lowercylindrical segment of the bore and has a flat underside or facet 74that is in direct physical contact with the upper active face of theflash LED 10. This maximizes heat extraction. A thermally conductivereflector 72 is inserted into the lower cylindrical part of the borebefore the sapphire sphere 12 is inserted.

In the embodiment of FIG. 7, the sapphire sphere 12 is snugly insertedinto a hole in a thin metal face plate 80, and sits on top of the flashLED 10. A thermally conductive fluid 82, preferably with a lowviscosity, is circulated via pump means (not illustrated) in a channelor conduit formed between the face plate 80 and the PCB 14. The fluidflows around the sides of the sapphire sphere 12 as indicated by thearrows 84, providing a heat exchanger. The flash LED 10 can be supportedon a pair of either separate or insulatively joined posts (notillustrated) to maximize convective or forced flow of cooling fluid pastthe flash LED 10. The cooling fluid can flow by convection instead ofactive pumping. The embodiment of FIG. 7 can provide enhancedperformance of the flash LED 10 even where the sapphire sphere 12 iseliminated and replaced with a window having minimal heat transferproperties.

Referring to FIG. 8, the sapphire sphere 12 is first press fit into abore in an aluminum face plate 92, which is thereafter anodized toprovide protective anodize layers 90. However, importantly there is noanodize layer 90 where the face plate 92 contacts the sapphire sphere 12to ensure maximum heat transfer. The growth of the anodize layer 90helps lock the sapphire sphere 12 in position at lock points 94. Theface plate 92 is in direct thermal contact with, but electricallyinsulated from, Copper traces 96 on PCB 14 by direct contact withanodized surface 98. A metal plate 100 backs the PCB 14 to providefurther heat transfer. In the preferred embodiment, a hard type IIIanodize surface is used for greater corrosion resistance, using any ofthe known sealing methods such as dichromate, nickel acetate and hotwater.

A further aspect of the present invention involves the use of theanodized coating as an electrical insulating layer between theconductive traces 96 on the PCB 14 and the anodized aluminum face plate92. Bare, large surface area conductors can be used on the LED side ofthe PCB 14 and held in mechanical contact with the insulating surface ofthe face plate 92 to maximize thermal contact. The anodized layers 90can be made very thin and therefore provide very good thermalconductors. The thermal grease 16 provides even further heat transferefficiency. Extra thick copper traces 96 can further enhance heatextraction.

Conventional techniques to remove backside heat from the PCB 14 can alsobe used in addition to those illustrated. The efficiency and operatinglife of the flash LED 10 are improved if its operating temperature canbe reduced. Conventional techniques include heavy copper traces, metalcores in the PCB 14, the inclusion of thermal vias, thermal fillers(T-Lam), multi-layer PCBs with copper flood planes, and conventionalheat sinks.

Referring to FIG. 9, the sapphire sphere 12 is supported on the concaveupper reflective surface 112 of a thermal cup 110. The flash LED 10 ismounted in receptacle in the thermal cup 110 and is held via solderjoints 114. A wire 118 is held by a solder joint 116 to the underside ofthe flash LED 10. The wire has an optional insulator jacket 120 andextends through a central hole in the thermal cup 110 and is soldered tothe PCB 14. A metal filler 122, which may be low melting point metal orsolder, may join the periphery of the flash LED 10 and the walls of thereceptacle in the thermal cup 110.

The shape of the beam formed by the transparent element 12 can beadjusted by various means. Where the transparent element 12 is asapphire sphere and mounted completely or partially in a socket orrecess in a front plate such as 80, the region above the transparentelement 12 can be filled with a transparent compound. If this compoundhas a flat outer surface the beam will be spread into a wider, lessfocused beam. The higher the index of refraction of the pottingmaterial, the less focused, and hence the wider the beam will be.Alternately, a polished flat or facet can be ground or otherwise formedon the upper side of the sapphire sphere 12 before installation into theface plate 80. Generally, although not necessarily, the plane of thisfacet would be parallel with the outer plane of the face plate 80. Thefacet could be a small area at the apex of the sapphire sphere or a muchlarger facet if the sapphire is a hemisphere. The larger the area of thefacet, the less focused the beam will be. The upper and/or lowersurfaces of the transparent element 12 could be frosted by chemicaletching or mechanical techniques such as sandblasting to diffuse andsoften the beam. The lower apex of the transparent element 12 can beground or polished to provide a small facet having an area that isapproximately the same as the emitter area of the flash LED. In general,it has been found that larger diameter sapphire spheres provide higheroptical coupling efficiencies (brighter beams) and smaller sapphirespheres produce more tightly focused beams. It is preferable to removethe reverse voltage protection die on the flash LED 10 in order toachieve maximum thermal coupling.

Over a range of about thirty to forty-five degrees, from the normal(Z-axis) to the face plate 80, the beam can be steered simply bylaterally shifting (in X and Y) the position of the flash LED 10relative to the central axis of the bore in the face plate 80. Thisresults in greater de-focusing and an increasing separation between thesapphire sphere 12 and the flash LED 10. This may impair heat transfer,but this can be offset by introducing a component of Z axis movement incombination with X-Y scanning to keep the flash LED 10 as close aspossible to the surface of the sapphire sphere 12.

Referring to FIG. 10, the sapphire sphere 12 is mounted on a thermalreflector cup 130 supported on PCB 14 which is carried by a mechanicalpivot (not illustrated). This construction allows the sapphire sphere 12to swivel inside the bore or socket formed in face plate 80 as indicatedby the arrow 134. Tilt angle 132 is the angle between light rays 30 andthe plane of the upper surface of the face plate 80, also indicated astheta. A spring 136 biases the sapphire sphere 12 to a pre-determinedangular orientation.

A pair of oppositely wound, flat spiral springs (not illustrated) canprovide compliant mounting force needed to hold the flash LED 10 againstthe sapphire sphere 12, while at the same time providing an electricalconnection to the PCB 14.

A larger sapphire sphere could be combined with a plurality of flashLEDs 10 (not illustrated) mounted in an array on one hemisphere or asection of the hemisphere. The beam projected from each flash LED may ormay not overlap the beam from an adjacent LED 10.

RGB arrays of flash LEDs 10 can be employed to allow multi-colored beamsto be produced. While presently only available in white, it isanticipated that flash LEDs of the type identified herein will beavailable that emit light in various colors. The phosphor coating on thecommercially available flash LED 10 can be removed after SMT to PCB toproduce a blue light emitting device.

Referring to FIG. 11, the sapphire sphere 12 is supported on the upperend of a thermal cup 146, whose hollow post is received in a hole in thePCB 14 that is slidable transversely as indicated by arrows 140. Aspring 142 surrounding the post biases the sapphire sphere 12 againstthe walls of the hole in the face plate 148. A wire 144 connects to theflash LED 10 and extends through the center of the post so that itsother end can be connected to the PCB 14.

Referring to FIG. 12, an embodiment is illustrated in which ahemispherical transparent element 150, which may be made of sapphire, isbonded on top of the flash LED 10 and the PCB 14 via adhesive 152. Alayer of potting compound 154 surrounds the transparent element 152,further solidifying the position and attachment of the transparentelement 150 to the PCB 14.

FIGS. 13 and 14 illustrate a commercially available high intensity LEDand lens assembly 160 available in the United States from LumiledsLighting US, LLC under the designation LUXEON® K2. The LED 162 (FIG. 14)is mounted on top of a small block portion 164 that supports leads 166.The LED is enclosed in a somewhat rigid, but still pliant, transparentdome-like cover 168 made of silicone rubber (FIG. 14). A quantity 170 ofa transparent silicone gel encases the LED 162 and is constrained withinthe cover 168. A solid frusto-conical lens 172 fits over the cover 168.A central passage 174 in the lens 162 forms a convex lens 176 which isused for beam formation.

Referring to FIGS. 23 and 24, the high intensity LED and lens assembly160, without the lens 172, can be placed in a pocket 176 (FIG. 24)formed in the underside of a holder 178 which allows the cover 168 toproject through a central circular aperture. A sharp blade 179 may thenbe used to cut off the upper section of the cover 168, without damagingthe underlying LED 162. Other techniques for safely removing the cover168 without damaging the LED 162 will occur to those skilled in the art,such as laser trimming, water jet cutting, hot wire cutting, andslicing. Once the upper section of the cover 168 has been removed, theremaining portion of the LED and lens assembly 160 can be used toconstruct the LED and lens assemblies illustrated in FIGS. 15-22.

The embodiment 180 of FIGS. 15 and 16 utilizes a spherical sapphire lenselement 182 which can be held in position above the LED 162 theremaining lower section of the cover 168. The remaining portion of thetransparent liquid gel 170 provides a thermal and optical interfacebetween the LED 162 and the spherical lens element 182. Referring toFIGS. 17 and 18, the embodiment 184 is similar to the embodiment ofFIGS. 15 and 16, except that in the embodiment 184 a truncated,spherical sapphire lens element 186 is utilized. The lens element 186has an upwardly facing facet 188. Referring to FIGS. 19 and 20, anotherembodiment 190 has a hemispherical sapphire lens element 192 with anupwardly facing facet 194. Referring to FIGS. 21 and 22, anotherembodiment 196 has a hemispherical sapphire lens element 198 with adownwardly facing facet 200 (FIG. 22).

The high intensity LED and lens assemblies of FIGS. 15-22 provideenhanced heat dissipation from the upper side of the LED 162.Furthermore, the sapphire lens element in each of these embodimentsprovides improved beam patterns, particularly when these high intensityLED and lens assemblies are immersed in a fluid such as water. Thismakes them particularly suited for underwater applications. The gel 170must be a thermally conductive, transparent material with suitableviscosity. However, this material must not change color in the presenceof high temperatures, such as 180° Centigrade. Silicone gel or greasehas been found to be particularly suited for providing the thermal andoptical interface between the LED 162 and the sapphire lens element.

The spherical lens element may also be made of Cubic Zirconia with ahigh index of refraction, such as N=2.17. Whereas a spherical sapphirelens may create some secondary rings of light in the beam outside of themain central focus, the beam produced by a spherical lens element madeof high index of refraction Cubic Zirconia is much cleaner. The CubicZirconia spherical lens element produces a high efficiency beam of lightwith superior control. More particularly, the use of such a CubicZirconia spherical lens element with a high lumen LED produces a focusedconvergent beam that allows one to easily add a molded plastic optic tocollimate or diverge the beam to essentially any beam angle from anarrow spot to a wide flood.

Regardless of what material the spherical lens element is made of,preferably the surface of the spherical lens element is mounted adjacentthe light emitting surface of the LED no further than twice the longestdimension of the light emitting surface. In addition, the spherical lenselement should have an index of refraction relative to the light emittedby the high lumen LED greater than about 1.65. Moreover, excellentresults can be achieved by using a spherical lens element having adiameter D greater than about three times the longest dimension of thelight emitting surface. The light path optical space between thespherical lens element and the light emitting surface of the adjacenthigh lumen LED is preferably filled with an intervening opticallytransparent material selected from the group consisting of fluid, gel,elastomer or rubber-like material, having an index of refraction lessthan about 1.50.

A high index of refraction lens element material is particularly suitedfor underwater lighting applications using LED light sources, where, forexample, N should be greater than about 1.6. When a spherical lenselement is submerged in a fluid or plotting compound its refractivepower is greatly reduced and therefore, the spherical lens elementshould be made of a material having a much higher index of refraction. Ahigh index of refraction material is needed when a rear or lower side ofa spherical lens element is pressed against silicone gel or otherinterface material covering the face of the LED.

Referring to FIG. 25, another embodiment of an LED illumination device202 utilizes a LEXEON LED 204 including a block portion 206. A generallyspherical lens element 208 is supported on top of the remaining section210 of the dome-shaped cover resulting from the fabrication processillustrated in FIGS. 23 and 24. The spherical lens element 208 ispreferably made of Cubic Zirconia having an index of refraction which isgreater than about 1.65. A quantity of an intervening opticallytransparent incompressible material 212 joins an upper light emittingsurface of the LED 204 with the underside of the spherical lens element208. This optically transparent material is preferably selected from thegroup consisting of fluid, gel, elastomer or other rubber-like material,and preferably has an index of refraction of less than about 1.50. Wherethe illumination device 202 is fabricated in accordance with the processillustrated in FIGS. 23 and 24, the intervening optically transparentmaterial 212 is silicone gel which is suitable for high temperatureapplications, i.e., 180° Centigrade or higher, because it does notdiscolor. Furthermore, silicone gel has desirable optical transmissioncharacteristics. In addition, the intervening optically transparentmaterial 212 helps draw heat from the LED 204 to the spherical lenselement 208 for dissipation therefrom. The spherical lens element 208could also be made of Zircon, Sapphire or SF8 Optical Glass. The spacingor distance Y between the spherical lens element 208 and the lightemitting surface of the LED 204 is important in determining theefficiency in gathering of light from the LED 204. Preferably, thedistance Y is less than twice the longest dimension of the lightemitting surface of the LED 204. In addition, the diameter of thespherical lens element 208 is also important in terms of the efficiencyof dissemination of light from the LED 204. Preferably, the diametershould be greater than about three time the longest dimension of thelight emitting surface of the LED 204. In actual devices constructedwith LUXEON LEDs a suitable diameter is about 9.5 millimeters. A secondoptical element such as lens 260 (FIG. 32) can be mounted adjacent thespherical lens element 208 to form a collimated beam. Lens 260 can bemolded out of acrylic or other suitable material. The second opticalelement can take a wide variety of configurations, as is well known tothose skilled in optics, depending on the beam pattern desired.

Referring to FIGS. 26 and 27, another embodiment of an LED illuminationdevice 214 includes a substrate 216 such as a printed circuit board,ceramic substrate, polyamide substrate, etc., with at least one apertureformed therein through which a metal heat sink 218 extends. The metalheat sink 218 contacts an exposed metal heat conduction surface 220 onthe underside of block portion 206. One or more metal disc springs 222are compressed between a lens retaining plate 211 and a cylindricalcollar 224. The collar 224 is compressed against block portion 206 tomaintain the heat conduction surface 220 in contact with heat sink 218.Any known means such as machine screws maybe used to load plate 211against the disc springs 222. The heat sink 218 may be made ofinsulating anodized Aluminum, Copper, Copper alloy or insulated Copperalloy. The LUXEON K2 LEDs require that heat sink surface 220 beelectrically insulated from LED connections 207 and 209 as well as anyother adjacent LEDs in the array. The insulation on the Copper alloy maytake the form of a diamond film. The disc springs 222 and collar 224provide a mechanism that clamps the heat conduction surface 220 againstthe heat sink 218 to ensure that the maximum amount of heat isdissipated from the LED 204. The heat sink 218 may take the form of ananodized Aluminum pin press fit into a larger planar heat sink 228through a suitably sized clearance aperture in the substrate 216.Preferably, the disc springs 222 are made of Beryllium Copper. Theinsulation barrier may be formed by an anodized layer on the sides andbottom of pin 218 allowing the top of pin 218 that is in contact withsurface 220 to be bare Aluminum for improved heat conduction. Similarly,an insulating layer on the sides and bottom of a Copper pin may be usedand thermal conduction surface 220 may be soldered to the top of theCopper pin.

The substrate 216 (FIGS. 26 and 27) can support multiple surface mountedLEDs each having their own associated spherical lens elements 208 andheat sink pins 218 extending through corresponding apertures in thesubstrate 216. Each of these multiple heat sink pins 218 can be pressfit into a corresponding socket in the larger underlying heat sink 228.

Referring to FIG. 28, another embodiment of an LED illumination device230 is specially adapted for immersion in a body 232 of fresh water orsalt water. The spherical lens element 208 is mounted in anhemispherical socket of an acrylic window 234. The window 234 preferablyhas an index of refraction greater than about 1.20. An interveningoptically transparent material such as silicon gel 236 joins the uppersurface of the spherical lens element 208 to the walls of thehemispherical socket in the window 234. Instead of water or seawater232, the fluid in which the embodiment 230 is immersed could compriseother optically transparent liquids such as mineral oil, Fluorinert™fluid manufactured by 3M, or Novec™ fluid manufactured by 3M. Therefraction of light from the LED 204 by the various optical elements andmedia is illustrated diagrammatically in FIG. 28 by a pair of lightrays.

Referring to FIG. 29, another embodiment of an LED illumination device238 has a spherical lens element 240 preferably made of Cubic Zirconiaand arranged with a modified Luxeon LED package 242 fabricated inaccordance with FIGS. 23 and 24, along with a second optical element243. The second optical element 243 has a negative focal length in orderto form the light into a light beam with a predetermined pattern asindicated diagrammatically in FIG. 29 by the light rays. The negativefocal length optical element may have a cylindrical component to changean aspect ratio of the light beam. Preferably, the spherical lenselement 240 has an index of refraction greater than about 1.80. It isalso possible to have a plurality of different optical elements in frontof a single spherical lens element 240, or in front of a plurality ofspherical lens elements 240 each having their own associated LEDpackages 242. The space between lens element 240 and second opticalelement 243 may be filled with a transparent fluid, gel, grease orpotting compound (not shown), to improve optical coupling and providefurther refractive control of the output light beam.

Referring to FIG. 30, another embodiment of an illumination device 244is similar to embodiment 238, except that the former employs a prismaticlens element 246 for bending the light as indicated diagrammatically inFIG. 30 by the light rays. The embodiment 244 is particularly suited foruse in automobile headlight assemblies. The light is re-directed fromthe LED 242 off of the vertical axis extending through the sphericallens element 240.

Referring to FIG. 31, another embodiment of an LED illumination device248 is designed to provide nearly hidden flush mount light sources. Thespherical lens element 208 preferably has, again, an index of refractionof greater than about 1.80 to converge the light to a focus. Ahemispherical second optical element 250 fits on top of the sphericaloptical element 208. Planar member 252 is placed above the hemisphericaloptical element 250 leaving an air gap having an index of refraction ofabout 1.00. Light emitted by LED 204 is collected by the spherical lenselement 208 and focused by the optical element 250 through a pin holeaperture 254 in the planar member 252. The embodiment 248 isparticularly suited for ceiling lighting, security lighting,illuminating wall art, etc. Element 250 serves to prevent total internalreflect (TIR) of the light exiting element 208. TIR light trappinginside the spherical lens element 208 can reduce the light transferefficiency of the LED lighting system.

Referring to FIG. 32, another embodiment of an LED illumination device256 includes a metal sleeve or spacer 258 between the LED device 242 andthe spherical lens element 208. The inside circular wall of the sleeve258 is reflectorized with suitable material (not illustrated) to reducelight loss. A second optical element 260 in the form of a circular orrectangular plastic lens has a hemispherical socket in optical contactwith the spherical lens element 208. The second optical element 260 ismade of a suitable material having an index of refraction of greaterthan about 1.50.

FIGS. 33-37 illustrate a thru-hull light assembly 262 utilizing variousconcepts previously described. A plurality of LED assemblies 264 (FIG.37) are mounted behind a transparent window 266 (FIGS. 33 and 36). Eachof the LED assemblies 264 is constructed in accordance with embodiment226 of FIGS. 26 and 27. The LED assemblies 264 are mounted within agenerally cylindrical housing 228 (FIGS. 35 and 36). The window 266 issealed to the housing 228 via O-ring 270. Housing 228 and window 266 aremounted inside and held by flange ring 268. Housing 228 is in turnsupported on threaded shaft 278 for external mounting on the hull 273 ofthe vessel. A central drum of the housing 228, as well as threaded shaft278, passes through a small hole in the hull of the vessel. A nut 276can be tightened on a threaded shaft 278 to press washers 280, 282, 284and 286 against the inside surface of the vessel hull. The threadedshaft 278 is forced through the small hole in the vessel hull to presshull insulator 272 (FIGS. 34-36) against the external surface and thesmall hole in the vessel hull. The hull insulator 272 serves to boththermally and electrically isolate light assembly 262 from the vesselhull. The threaded shaft 278 is sealed into the drum on cylindricalhousing 228 and provides a water-tight pathway for electrical conductors289 that supply power to the LED assemblies 264. Screws 213 (FIG. 35)hold plate 211 against housing 228.

The thru-hull illumination device 262 (FIGS. 33-37) has the advantage ofbeing low profile, permitting it to be mounted to the outside surface ofthe vessel hull without creating undo drag. The LED assemblies 264provide substantial underwater lighting for purposes of photography,observing submerged obstacles, attracting fish, aesthetic qualities andso forth. The LED assemblies 264 may produce all white light, or theymay be red, green and blue, which, in various combinations ofenergization, can produce a beam of light of a desired color.

FIGS. 38 and 39 illustrate a preferred embodiment of an LED illuminationdevice 288 which is similar to the embodiment 202 of FIG. 25, exceptthat in the former a rod lens element 290 is used in place of thespherical lens element 208. The rod lens element 290 has a curved lowersurface 292 (FIG. 39) which gathers light from the LED device 242. Therod lens element 290 has a flat upper surface 294.

Referring to FIGS. 40 and 41, another embodiment of an illuminatingdevice 296 is similar to the embodiment 288 of FIGS. 38 and 39, exceptthat the former utilizes a rod lens element 298 with curved upper andlower surfaces 300 and 302.

While various embodiments of improved LED illumination devices have beendescribed in detail, it will be apparent to those skilled in the artthat the invention can be modified in both arrangement and detail. Forexample, the lens element that directly gathers light from the highintensity LED 204 can have varying shapes and configurations; however,preferably the underside surface is round, ellipsoid, parabolic or someother curved surface for gathering the light. As another example, theembodiments of FIGS. 1-12 and 15-22 could have optical elements adjacentthe LEDs that are made of Sapphire, Cubic Zirconia, Zircon or SF8optical glass. The heat sinks that extend through the apertures in thePCB substrate can be made by any known means. For example, rather thanbeing pressed into place, these can be raised machined or formedfeatures in a solid metal plate. TIR in a Cubic Zirconia spherical lensor ball can be reduced or eliminated by coating the surfaces with amaterial with an index of refraction intermediate between, for example,air with an index of refraction of 1.0 and the Cubic Zirconia at 2.17.E-Beam Quartz is an example of such a coating. LUXEON K2 LEDs areavailable in green, cyan blue and royal blue colors. Various proportionsof each color may be used to maximize the attraction of marine life.Therefore, the protection afforded the invention should only be limitedin accordance with the following claims.

1-52. (canceled)
 53. An illumination device, comprising: a lightemitting diode; a generally hemispherical shaped lens having a flatsurface positioned adjacent to a light emitting surface face of thelight emitting diode; and the hemispherical shaped lens having an indexof refraction relative to light emitted by the diode greater than about1.65.
 54. The illumination device of claim 53 wherein the flat surfaceof the hemispherical shaped lens is in contact with the light emittingsurface face of the light emitting diode.
 55. The illumination device ofclaim 53 wherein the flat surface of the hemispherical shaped lens ispositioned within a predetermined distance from the light emittingsurface face of the light emitting diode, the predetermined distancebeing less than or equal to a diameter of the hemispherical shaped lens.56. The illumination device by claim 53 and further comprising anintervening optically transparent material selected from the groupconsisting of fluid, grease, gel and elastomer having an index ofrefraction of less than about 1.50, the material filling a space betweenthe flat surface of the hemispherical lens and the light emittingsurface face of the light emitting diode.